What is the role of Auto-smooth?
With Blender 2.80 the use of the Edge Split modifier is deprecated in favor of new custom normals.

Custom Normals allow precise tweaking of normals beyond what auto-smooth can do 

There's a lot more information in the Normals section of the recent documentation site. Although I'm not a big copy-n-paster, this is what it has to say about Auto-Smooth:


  The Auto Smooth option is a quick and easy way to combine smooth and faceted faces in the same object.


In addition, when you use custom normals:


  This has the side effect of enabling Auto Smooth, as that is necessary to use custom normals. Once you have custom normals, the angle threshold of the Auto Smooth behavior is disabled – all non-sharp-tagged edges will be considered as smooth, disregarding the angle between their faces.


Which brings us to the link to the documentation for Auto-Smooth:
https://docs.blender.org/manual/en/2.80/modeling/meshes/structure.html#auto-smooth